This invention relates to a material for diffusion transfer and, more particularly, to a photosensitive material for the silver complex diffusion transfer.
The principle of the silver complex diffusion transfer process (hereinafter referred to as DTR process) is described in U.S. Pat. No. 2,352,014 and is well known. It is also known that in order to produce a transferred silver image of high contrast and high sharpness on an image-receiving layer, a rapid formation of the transferred silver is necessary. Further, another common means for the formation of a transferred silver image of high sharpness is the utilization of an antihalation layer. As is known well, a black pigment such as carbon black is preferentially used in the antihalation layer of silver halide photographic materials for DTR process, because the black pigment such as carbon black absorbs light over the entire wave length range and because in the photographic materials used in DTR process there is no need to remove the color of antihalation layer by leaching or bleaching during processing steps. However, although effective in improving the sharpness and resolution of a transferred silver image, the antihalation layer has a disadvantage of markedly decreasing the photosensitivity. Further, it is important for a photosensitive material used in DTR process to retain the image reproduction characteristics which permit the photosensitive matrial to reproduce as faithfully as possible the image of an original such as, for example, that involving fine lines of several tens microns in width, particularly when the original contains both the fine lines (black lines) in positive image on a white background and the fine lines (white lines) in negative image on a black background. The image reproducibility is found to become inferior particularly when the photosensitive material has a sensitivity sufficient for photographing an original by the camera work.
The reduction in photosensitivity caused by the antihalation layer can be avoided to a large extent, as described in U.S. Pat. No. 4,144,064, by providing between the antihalation layer and the silver halide emulsion layer an intermediate layer containing a white pigment such as titanium dioxide. There is also known a material for DTR process, wherein an antihalation layer and a white pigment layer are provided, in the order indicated, on a support and overlaid with a silver halide emulsion layer. Although having an advantage of reproducing an image excellent in sharpness and resolution, without a large decrease in sensitivity, such materials for the diffusion transfer process were found to have the following various disadvantages: The antihalation layer of such a material contains a reduced amount of a black pigment per unit area and, when overlaid with a layer of a large amount of a white pigment, tends to reveal unevenness in the coating and occurrence of streaks on the surface. Part of the black pigment sometimes diffuses into the white pigment layer to decrease the hiding power of the white pigment, to decrease the photosensitivity, or to cause uneven density, thus making it comparatively difficult to manufacture a photosensitive material with satisfactory reproducibility. The drying of the antihalation layer and the white pigment layer consumes a good amount of heat energy and, in addition, the dried pigment layer causes a reduction in the adherence of the layer to a hydrophilic colloid layer such as, for example, a silver halide emulsion layer, resulting in even poor adhesion of the emulsion to the white pigment layer in coating operation. When the diffusion transfer development is performed by using the defective photosensitive and image receiving materials, at least one of the above disadvantages gives rise to the occurrence of streaks on the image-receiving material caused by the faulty transfer.